In recent years, information and telecommunications networks based on IP (Internet Protocol) technology are rapidly spread and widely used. In particular, the information and telecommunications network using Ethernet (registered trademark) is spreading rapidly as the wide area Ethernet (registered trademark) service. And, the network construction technology of the information and telecommunications network is shifting to NGN (Next Generation Network) by leading with the packet-switched network.
However, circuit-switched apparatuses based on the connection oriented technology, such as an ATM (Asynchronous Transfer Mode) technology or a TDM (Time Division Multiplex) technology, are still used in many Common Carrier networks and Private Business networks. And, it is also strongly required to provide services using these legacy facilities of the circuit-switched network in the packet-switched network from an economical point of view.
Patent document 1 (Japanese Patent Application Laid-Open No. 2007-184681) discloses an ATM converter which is capable of providing broadband and cheap communication services by connecting ATM apparatuses transmitted in multi spots to the information and telecommunications network using Ethernet (registered trademark). This ATM converter includes an ATM interface, an Ethernet interface and a media converting means. This ATM converter converts ATM cells supplied from the ATM apparatus into Ethernet frames and transmits the converted Ethernet frames to the wide area Ethernet (registered trademark) network. This ATM converter also converts Ethernet frames received from the wide area Ethernet (registered trademark) network into ATM cells and supplies them to the ATM apparatus.
On the other hand, in the field of the mobile communication, data communication is increasing rapidly in a so-called mobile backhaul area. The mobile backhaul area is a mobile access network which connects between BTS (Base Transceiver Station) and BSC/RNC (Base Station Controller/Radio Network Controller) in 2G (Second Generation Mobile System) and 3G (Third Generation Mobile System). This rapid increase phenomenon of data communication in the backhaul area is mainly caused by sudden augmentation of demand for a music distribution service, a video download service and other new services relating to multimedia.
In the mobile backhaul area, facilities using the ATM technology and the TDM technology are intermingled with each other. Therefore, network management works are becoming more complicated and the extension of facilities itself in the mobile backhaul area is also becoming in a difficult situation. From such reasons, there is a movement of constructing a mobile communication network using ALL-IP technology, i.e., ALL-IP mobile communication network, in which communication protocols of the backhaul network and the backbone network are integrated into the IP protocol. This movement aims at efficiency of network facilities and practical operation. And, a solution for being migrated to the ALL-IP mobile communication network is desired while keeping existing facilities in the mobile backhaul area as they are.
As a means for being migrated to the ALL-IP technology network while keeping existing facilities as they are, PWE (Pseudo Wire Emulation) technology is highly expected which transmits data generated by facilities of the TDM/ATM technology on the IP based network.
PWE is a technology proposed by IETF (The Internet Engineering Task Force). And, it is defined as “PWE3 (Pseudo Wire Emulation edge to edge) is a mechanism which emulates the basic attribute in the service like ATM, frame relay or Ethernet over packet-switched network (PSN)”.
Patent document 2 (Japanese Patent Application Laid-Open No. 2006-229985) discloses technology which provides an automatic PW (Pseudo Wire) peer detection mechanism in an Ethernet based network. This technology can acquire MAC (Media Access Control) address of a partner PW peer in a far end by exchanging information with the partner PW peer.
However, there is a problem to be settled in order to construct a system which transmits data generated by the existing facilities of TDM/ATM technology on the packet-switched network while keeping existing facilities as they are. The problem is caused by difference in a concept of network reliability between the packet-switched network and the circuit-switched network. That is, the packet-switched network is not sufficient in an aspect of communication quality control while the circuit-switched network such as the TDM/ATM network is provided with the high reliability of communication quality control.
For example, the APS (Automatic Protection Switching) function is an indispensable function in the circuit-switched network. The APS function is a function to improve stability and easiness in a maintenance aspect and a service operation aspect for a communication network by providing an active line and a standby line as a redundant configuration, and the active line and the standby line are changed over appropriately. Patent document 3 (Japanese Patent Application Laid-Open No. 2002-261798) discloses technology about an ATM line switching apparatus by the APS function.
When constructing the system which transmits data of the TDM/ATM apparatus on the packet-switched network, it is desirable to introduce the APS function for improving stability and easiness in the maintenance aspect and the service operation aspect for the system. The APS function is required at least a TDM/ATM line interface side, i.e., a circuit-switched network interface side, in a network connection apparatus which interconnects the circuit-switched network and the packet-switched network respectively.
When the APS function is introduced by the redundancy configuration of “1+1” basis, two transmission lines of the active line and the standby line are provided at the circuit-switched interface side, i.e., between the network connection apparatus and the TDM/ATM apparatus, and transmits the same data simultaneously on the active line and the standby line. And, it is necessary to change over instantaneously the active line and the standby line when a failure has occurred in the active line. That is, the line used to be an active state has become a standby line having been switched and the line used to be a standby state has become an active line having been switched when changeover of the APS function has been performed under the redundancy configuration of “1+1” basis.
However, when the APS function is introduced into the system which transmits data used in the circuit-switched network on the packet-switched network, there is a problem that the APS function does not operate normally due to a concept of MAC address. This is because that MAC address is necessary information for a routing operation performed in the packet-switched network but the concept of MAC address does not exist in the circuit-switched network such as the ATM/TDM network.